Help Solving Trig Equation: Cos70°cos20°-sin70°sin20°

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Homework Help Overview

The discussion revolves around simplifying the trigonometric expression cos70°cos20° - sin70°sin20°, focusing on the application of trigonometric identities. Participants are exploring the relationships between the angles involved.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the use of the cosine addition formula and question the equivalence of the angles involved. There is also uncertainty about identifying basic angles related to 70° and 20°.

Discussion Status

Some participants have referenced the cosine addition formula, while others are clarifying their understanding of angle equivalences. There is an acknowledgment of a potential relationship between the angles, but no consensus has been reached on the simplification process.

Contextual Notes

Participants express difficulty in identifying equivalent angles and seem to be operating under the constraints of homework guidelines that may limit the use of certain resources.

CrossFit415
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Cos70°cos20°-sin70°sin20°

I can't find any of these angles that are equivalent to the basic angles. Thanks
 
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Do you know a formula for cos(a+b) in terms of the trig functions evaluated at a and b?
 
Cost(a+b)=cos a • cos b - sin a • sin b
 
I don't know which angles are equivalent to 70° nor 20°
 
But you know cos(20+70)=cos(90), right?
 
Whoops. Thanks
 

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